Vacuum assisted molding methods are well known in the art for forming resin-fiber composite structures. Traditionally, however, the formation of such structures has been limited to panels and other like-shaped structures. Complexly shaped structures, such as a portion of a skin and an associated stiffener, have heretofore been difficult, if not impossible, to produce from traditional composite molding systems and methods in a single molding step because such complex structures are difficult to “lay up”. By “lay up”, it is meant arranging a plurality of fiber plies (i.e., layers) into a single fiber preform. As such, the manufacture of various complexly shaped structures has typically involved forming two independent composite laminate structures through the well known vacuum molding process, and then securing the structures together via rivets or other like mechanical fasteners in a separate manufacturing step.
Various attempts have been made to bond two or more completely formed composite laminate structures together via a suitable adhesive. U.S. Pat. No. 4,786,343, assigned to The Boeing Company, discloses various methods for bonding two or more composite laminate structures together via an adhesive. While these methods have proven effective in bonding a wide variety of complexly shaped composite laminate structures, it would nevertheless be desirable to provide a system and method in which the bonding of two or more complexly shaped composite structures can be accomplished on a suitable tool, in a single manufacturing operation, using an otherwise conventional vacuum assisted resin transfer molding process. More specifically, it would be highly desirable to provide a system and method in which dry fiber preforms (i.e., multi-layer preforms that have not yet been preimpregnated with resin) can be placed on a suitable tool with the preforms precisely aligned in the desired orientation relative to one another, with an adhesive material placed at the desired bond line(s), and the bonding of the preforms together accomplished immediately prior to infusing the preforms with resin, and all with a single manufacturing operation. This would eliminate the added labor associated with subsequently taking the finished composite laminate component pieces and precisely aligning same, in a separate manufacturing step, prior to adhering the independent component pieces together. It is further expected that a system and method which accomplishes heating and flowing of the adhesive into the surfaces of two or more independent, dry fiber preforms, will produce even greater migration of the viscous adhesive into the plys of each of the preforms.